Field of the Invention
The invention relates to active noise control, and, in particular, to an auto-selection method and associated active noise control system for modeling secondary-path estimation filters capable of performing auto-selection of secondary-path estimation filters to compensate noise.
Description of the Related Art
The purpose of active noise control is to generate an anti-noise signal from a speaker to minimize or cancel the noise level of the original signal. Conventional noise control techniques use passive treatments to minimize the noise level. For example, the automobile industry minimizes the noise level in the car cabin by using mufflers to absorb the engine noise. These conventional noise control techniques can minimize noise that has a medium or high frequencies. However, these techniques cannot minimize noise that has a low frequency. With active noise control, an anti-noise signal with the same low frequency as the low-frequency noise signal can be produced. The phases of the anti-noise signal are opposite to those of the low-frequency noise signal. When the two signals reach the same point, they satisfy the superposition principle and negate each other.
The filtered-x least mean square (FxLMS) algorithm is the most popular adaptive algorithm for active noise control (ANC) systems, due mainly to its simplicity and robust performance. However, the convergence speed of the FxLMS algorithm is slow. Furthermore, its performance is degraded when there is a large measurement noise in the reference and error signals.
Accordingly, there is demand for an active noise control system and associated method to solve the aforementioned issue.